1. Field of the Invention
The invention relates generally to footwear and in particular to an article of footwear which contains a mechanism for enhanced cushioning by absorbing the shock of walking or running and which by pumping air through the footwear provides ventilation for drying and cooling of the foot by evaporation and convection.
2. Description of Related Art
There are two different yet interrelated aspects of the present invention, shock absorption and ventilation. In many cases, prior art has attempted to address the issue of shock absorption by the use of fluid-filled devices in or adjacent to the sole of the footwear. Guy 1069001, Caston, U.S. Pat. No. 6,282,815, Moore 508034 and Swigart 2005/0022422, all deal with shock absorption by the transfer of fluid, Several other patents; Lakic U.S. Pat. No. 5,025,575, Huang U.S. Pat. No. 5,341,581, Swigart 2005/0022422 and others, have internal valves to control the direction of airflow. Litchfield U.S. Pat. No. 6,505,420 provides for flow rate control. Johnson U.S. Pat. No. 4,446,634 controls the rate of flow and provides for adjustment.
In the prior art, systems for providing ventilation in footwear have attempted to address the issue of cooling and drying by removing excessive heat and moisture with a constant air exchange. Clark U.S. Pat. No. 6,247,248, Sanner 2002/0170203, Cintron U.S. Pat. No. 5,675,914 and others, allow for airflow. Guy 1069001, Swigart 2005/0022422 and Ahn U.S. Pat. No. 3,973,336 provide an air snorkel to overcome some of the issues surrounding particulate introduction.
An exhaustive search of prior art shows that there are many examples of footwear or shoe inserts that attempt to address the issue of shock absorption and ventilation in one manner or another. There are deficiencies found within prior art such as; problems with clogging of the intake conduits and valves by particulate matter introduced either externally or within the shoe cavity, moisture accumulation within the air channels and cavities and/or lack of proper fresh air flow, and a lack of control of the rate of air/fluid transfer. In cases where the air flow was restricted, it was through a simple constriction of the channel and there was no variable control of the rate of air flow. In the cases where there was control of the rate of air flow, the control only involved a restricted pressure release and could not absorb the short duration, high pressure spikes of the heel impact.
The present invention incorporates additional means to improve the absorption of shock by controlled pressure release and the improved ability to absorb high impact heel strikes. In addition the present invention provides for improved air flow, prevention of contamination of the mechanism and simplicity of manufacturing. The intent to achieve improved cushioning and comfort in footwear is thereby achieved.